refactor: move Std.Range to Std.Legacy.Range

[datokrat]

This PR renames the namespace Std.Range to Std.Legacy.Range. Instead of using Std.Range and [a:b] notation, the new range type Std.Rco and its corresponding a...b notation should be used. There are also other ranges with open/closed/infinite boundary shapes in Std.Data.Range.Polymorphic and the new range notation also works for Int, Int8, UInt8, Fin etc.

[leanprover-community-bot]

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• ❗ Reference manual CI will not be attempted unless your PR branches off the nightly-with-manual branch. Try git rebase 5339c47555cb65958259b1c4c4c687c3863a08be --onto 646df6ba16b3f68de539a085456c323e160e206d. You can force reference manual CI using the force-manual-ci label. (2025-12-13 00:18:07)